VOID FABRIC TENSOR AND ULTIMATE STATE SURFACE OF SOILS

This paper presents a method to characterize the fabric of soils. Atte ntion is focused on the directional distribution of voids in these mat erials. The mean porosity and void fabric tensor used in the descripti on are obtained by the stereological technique. The use of a void fabr ic index to quantify the variation of the fabric tensor with deformati on is highlighted. The fabric description is also used to expand the c ritical state soil mechanics framework. A proposal for an ultimate sta te surface of soils is made. The study shows that the representation o f the ultimate state surface is dependent on the choice of the set of pertinent state variables. Its representation in reduced state dimensi ons may not be unique. The study further shows that the initiation of strain-softening in soils is the result of structural collapse of the solid skeleton. The use of the void fabric index to identify the initi ation of collapse is explored.